1. Field of the Invention
The present general inventive concept relates to a semiconductor manufacturing apparatus, and more particularly, to an apparatus and method to generate plasma which can be applied to semiconductor processing.
2. Description of the Related Art
An etching process is a type of semiconductor manufacturing process which selectively removes some portions of a semiconductor layer under a patterned photosensitive film on a semiconductor substrate. The etching process can be generally classified into a dry etching process and a wet etching process. Recently, a plasma-based dry etching process has been developed to form fine semiconductor patterns having a size of microns or less in response to a high integration of a semiconductor device.
For the plasma-based dry etching process, with a reaction gas introduced into an air-tight chamber and then ionized into plasma, the plasma-based dry etching process is performed along patterns on a semiconductor substrate via an acceleration force and a chemical reaction of plasma ions.
One of the most general plasma generating apparatuses is an RF plasma generating apparatus which converts a reaction gas introduced into a chamber to plasma via an RF electric field generated when applying a high frequency power to electrodes positioned inside the chamber.
RF plasma generating apparatuses can be classified into a capacitively coupled plasma (CCP) generating apparatus, which generates plasma using characteristics of a capacitor formed between an upper and a lower planar electrode facing each other, and an inductively coupled plasma (ICP) generating apparatus, which generates plasma using characteristics of an inductor formed by an upper coil opposite a lower planar electrode.
The CCP generating apparatus has an advantage in that it has a higher etching selection ratio with respect to a photosensitive film than that of the ICP generating apparatus. However, the CCP generating apparatus has a disadvantage in that an electric discharge occurs only when a chamber pressure reaches a predetermined pressure of about 20˜50 mTorr or more, providing disadvantageous effects to an etching profile, and a disadvantage in that the plasma generated by the CCP generating apparatus has low density, thereby deteriorating an etching rate.
On the other hand, the ICP generating apparatus has an advantage in that, since the ICP generating apparatus can generate plasma at low pressures (1˜5 mTorr), it can more easily form micro patterns than the CCP generating apparatus, and an advantage in that since the plasma generated by the ICP generating apparatus has high density, it has a high etching rate. However, the ICP generating apparatus has a disadvantage of a low etching selection ratio due to a high temperature of electrons of the plasma generated by the ICP generating apparatus.
Accordingly, a new type of RF plasma generating apparatus has been recently developed, which combines the CCP apparatus and the ICP apparatus so as to compensate for the contradictory advantages and disadvantages of both apparatuses. Details of this RF capacitively and inductively coupled plasma generating apparatus are disclosed in U.S. Pat. No. 6,308,654.
The RF capacitively and inductively coupled plasma generating apparatus described in U.S. Pat. No. 6,308,654 includes a conical induction current coil positioned on an outer wall of an air-tight chamber so as to surround a plasma generating space defined between electrodes for the purpose of compensating for the disadvantage of the electrode discharge in the CCP apparatus, such that additional plasma is generated in the chamber by an electric field generated when applying a high frequency power to the conical induction current coil, thereby allowing high density plasma to be generated at low pressures.
The capacitively and inductively coupled plasma generating apparatus has an advantage of increasing the etching rate through an increase in plasma density within the chamber, but has a disadvantage in that, since the electric discharge by the induction current coil is generated in the plasma generating region, the etching selection ratio decreases due to a high electron temperature.
For an advanced semiconductor device, etching of an integrated circuit must be performed to have a narrow width and a high depth so as to form vias and contacts which have an aspect ratio of 5:1 or more. Thus, the reduction in the etching selection ratio causes the disadvantage of decreasing an etching efficiency as described above.